Running a tank with live rock and a skimmer is completely adequate. The key is to have enough rock, at the bare minimum I would suggest the 1 lb a gallon standard. You also need very good flow, so a power head at each end, I have 2 x 1200gph. You want strong flow through the rocks for filtration. And an over powered skimmer.
The ac hob is not required but if you like running chemical filtration to polish the water, minimize phosphate and further reduce organics then it gives you a place to put it. Mechanical filtration with a filter pad also polishes the water, and if you are diligent in replacing it can help maintain lower nitrates. You could also use the space to add additional biological filtration, like seachem matrix or marine pure. These products provide a huge surface area to grow beneficial bacteria. This is why I like running the ac.